#pragma once
#include <iostream>
#include <string>
#include <vector>
#include <fstream>
#include <unordered_map>
#include <mutex>
#include "util.hpp"
namespace ns_index
{
    struct DocInfo
    {
        std::string title;   // 文档标题
        std::string content; // 文档去标签后对应的内容
        std::string url;     // 官网url
        uint64_t doc_id;     // 文档id
    };
    struct InvertedElem
    {
        uint64_t doc_id;
        std::string word;
        int weight;
    };
    typedef std::vector<InvertedElem> InvertedList;

    class Index
    {
    private:
        // 正排素引
        std::vector<DocInfo> forward_index;
        // 倒排索引
        std::unordered_map<std::string, InvertedList> inverted_index;
        Index() {} // 不能delete
        Index(const Index &) = delete;
        Index &operator=(const Index &) = delete;
        static Index *instance; // 单例
        static std::mutex mtx;  // 锁
    public:
        ~Index() {}
        // 创建单例
        static Index *GetInstance()
        {
            if (nullptr == instance)
            {
                mtx.lock();
                if (nullptr == instance)
                    instance = new Index();
                mtx.unlock();
            }
            return instance;
        }
        // 查找文档
        DocInfo *GetForwardIndex(uint64_t doc_id)
        {
            if (doc_id >= forward_index.size())
            {
                std::cerr << "doc_id out range,error" << std::endl;
                return nullptr;
            }
            return &forward_index[doc_id];
        }
        // 获取倒排拉链
        InvertedList *GetInvertedList(const std::string &word)
        {
            auto iter = inverted_index.find(word);
            if (iter == inverted_index.end())
            {
                std::cerr << word << "    have no InvertedList" << std::endl;
                return nullptr;
            }
            return &(iter->second);
        }
        // 建立正排索引和倒排索引
        bool BuildIndex(const std::string &input)
        {
            std::ifstream in(input, std::ios::in | std::ios::binary);
            if (!in.is_open())
            {
                std::cerr << "sorry:  " << input << "open error" << std::endl;
                return false;
            }
            std::string line;
            //int count = 0;
            while (std::getline(in, line))
            {
                DocInfo *doc = BuildForwardIndex(line);
                if (nullptr == doc)
                {
                    std::cerr << "build" << line << " error" << std::endl;
                    continue;
                }
                BuildInxertedIndex(*doc);
                // count++;
                // if (count % 50 == 0)
                // {
                //     std::cout << "已经建立的索引文档： " << count << std::endl;
                // }
            }
            return true;
        }

    private:
        DocInfo *BuildForwardIndex(const std::string &line)
        {
            // 解析line
            std::vector<std::string> results;
            const std::string sep = "\3";
            ns_util::stringUtil::CutString(line, &results, sep);
            // 判断切割结果
            if (results.size() != 3)
            {
                return nullptr;
            }
            // 填充 DocInfo
            DocInfo doc;
            doc.title = results[0];
            doc.content = results[1];
            doc.url = results[2];
            doc.doc_id = forward_index.size();
            // 插入到正排素引
            forward_index.push_back(std::move(doc));
            return &forward_index.back();
        }
        bool BuildInxertedIndex(const DocInfo &doc)
        {
            // DocInfo{title, content, url, doc_id}
            // word -> 倒排拉链
            struct word_cnt
            {
                int title_cnt;
                int content_cnt;
                word_cnt() : title_cnt(0), content_cnt(0) {}
            };
            std::unordered_map<std::string, word_cnt> word_map; // 用来暂存词频的映射表
            // 对标题进行分词
            std::vector<std::string> title_words;
            ns_util::JiebaUtil::CutString(doc.title, &title_words);
            // 对标题进行词频统计
            for (std::string s : title_words)
            {
                boost::to_lower(s);      // 需要统一转化成为小写
                word_map[s].title_cnt++; // 如果存在就获取，如果不存在就新建
            }

            // 对文档内容进行分词
            std::vector<std::string> content_words;
            ns_util::JiebaUtil::CutString(doc.content, &content_words);

            // 对内容进行词频统计
            for (std::string s : content_words)
            {
                boost::to_lower(s);
                word_map[s].content_cnt++;
            }

#define X 10
#define Y 1
            for (auto &word_pair : word_map)
            {
                InvertedElem item;
                item.doc_id = doc.doc_id;
                item.word = word_pair.first;
                item.weight = X * word_pair.second.title_cnt + Y * word_pair.second.content_cnt; // 相关性
                InvertedList &inverted_list = inverted_index[word_pair.first];
                inverted_list.push_back(std::move(item));
            }
            return true;
        }
    };
    Index *Index::instance = nullptr;
    std::mutex Index::mtx; // 锁

}